Hope this may help you :)

```
class Solution
{
public:
int search(vector<int>& nums, int target)
{
int length = nums.size();
int left = 0, right = length - 1, mid;
int pivot = -1;
//decide whether there is a rotation
if (nums[0] > nums[length-1])
{
//find pivot
while (left <= right)
{
mid = (left + right) / 2;
if (nums[mid] >= nums[0])
{
left = mid + 1;
}
else if (nums[mid] < nums[0])
{
right = mid - 1;
}
}
pivot = left;
}
//find search range
if (pivot != -1)
{
if (target >= nums[0])
{
left = 0;
right = pivot - 1;
}
else
{
left = pivot;
right = length - 1;
}
}
else
{
left = 0;
right = length - 1;
}
//binary search
while (left <= right)
{
mid = (left + right) / 2;
if (nums[mid] == target)
{
return mid;
}
else if (nums[mid] > target)
{
right = mid - 1;
}
else
{
left = mid + 1;
}
}
return -1;
}
};
```